Those two ideas--the state of nature and the natural executive power to punish--are empirical claims about human nature and human history. Darwinian science can help us test those claims against the pertinent evidence.
I want to make a general point here about the study of political philosophy. Much of the study of the history of political philosophy is rightly devoted to studying the history of ideas. But ultimately shouldn't our primary concern be judging the truth of those ideas based on our assessment of the relevant evidence?
So, for example, Darwinian anthropology can confirm the reality of the state of nature as the original condition of humanity by showing how our earliest hunting-gathering ancestors lived in nomadic foraging bands, in which all adults lived as equally free individuals, aggressively defending their autonomy against bullies who might try to dominate them. This was the evolutionary state of nature in which human nature was shaped. Some of my posts on this can be found here and here, with links to others.
Some of the scholarly commentators on Locke would object that Locke saw the state of nature as a moral fiction rather than as a historical reality. John Dunn, for example, claimed that Locke's idea of the state of nature represents "neither a piece of philosophical anthropology nor a piece of conjectural history," because it has "no transitive empirical content whatsoever" (1969, 103). Other scholars see Locke's state of nature as both historical reality and moral fiction (Ashcraft 1968, 1987; Waldron 1989). And some others emphasize Locke's account of the state of nature as the natural history of primitive foraging bands like the American Indians (Myers 1998; Pangle 1988; Strauss 1953, 230-31).
The decisive evidence for Locke's state of nature as an anthropological historical reality is Locke's reliance on the many anthropological reports about the American Indians, which was part of the European intellectual interest in New World natural history arising from the European discovery of America (Arneil 1996; Batz 1974; Elliott 1972; Glat 1981; Martens 2016; Meek 2011). I have emphasized the importance for Locke of books such as Jose de Acosta's The Natural and Moral History of the Indies (ST, sec. 102). In his edition of Locke's Two Treatises, Peter Laslett provides footnotes with quotations from the books on America in Locke's library that echo Locke's description of the state of nature. Studying such books led Locke to declare: "In the beginning, all the World was America," and therefore it is a "Pattern of the first Ages in Asia and Europe" (ST, secs. 49, 108).
Here I will turn to Locke's account of the natural right to punish, which he calls the executive power of the law of nature. This will be followed by another post on the evidence from Darwinian anthropology supporting Locke's idea.
Locke claims that in the state of nature, there is a law of nature "that being all equal and independent, no one ought to harm another in his Life, Health, Liberty, or Possessions" (ST, sec. 6). But then he immediately qualifies this no-harm principle by saying that one may rightly harm another in punishing someone for an offense against the law of nature. This must be so because the law of nature could not be a true law if it were not enforced by punishment of those who violate it. Enforcing the no-harm principle requires harming those who would harm us.
In the state of nature, Locke explains:
"The Execution of the Law of Nature is in that State, put into every Mans hands, whereby everyone has a right to punish the transgressors of that Law to such a Degree, as may hinder its Violation. For the Law of Nature would, as all other Laws that concern Men in this World, be in vain, if there were no body that in the State of Nature, had a Power to Execute that Law, and thereby preserve the innocent and restrain offenders, and if any one in the State of Nature may punish another, for any evil he has done, every one may do so. For in that State of perfect Equality, where naturally there is no superiority or jurisdiction of one, over another, what any may do in Prosecution of that Law, every one must needs have a Right to do" (sec. 7).Notice that Locke does not rely on divine punishment to enforce the law of nature. The law of nature, like all the other laws that concern "Men in this World" would be in "vain" if individual human beings did not punish the offenders of that law. This punishment has two distinct purposes: restraint and reparation (secs. 8, 10-11). Punishing for restraint is to prevent or deter misconduct, and everyone has the right to punish for this purpose. Punishing for reparation belongs only to the injured party, who seeks some recompense for the damages he has suffered.
Locke indicates that this human punishment of offenders in the state of nature works at three levels. Through first-party punishment, individuals punish themselves through conscience and guilt (secs. 8, 21, 122, 209). Through second-party punishment, individuals punish their tormentor through retaliation and revenge (secs. 8, 10-11, 18-19). Through third-party punishment, individuals can join with those who have been injured unjustly for a collective punishment of the offender (sec. 10).
Locke suggests, however, that there are at least three problems with relying on the individual right to punish to enforce the law of nature in the state of nature (secs. 123-126).
First, there's the problem of knowledge: many individuals do not have a clear and unbiased knowledge of the law of nature. In the Letter Concerning Toleration (43), Locke says that the American Indians are "strict Observers of the Rules of Equity and the Law of Nature." But in the Second Treatise (sec. 123), he says that in the state of nature "the greater part" of men are "no strict Observers of Equity and Justice." In fact, some men are so "degenerate" that they have no knowledge of the law of nature, and they become like wild animals in their violent attacks on others (ST, secs. 10-11, 128).
Second, there's the problem of partiality: individuals being partial to themselves often cannot render impartial judgment in their own cases, and they are often negligent or unconcerned in judging the cases of others.
Third, there's the problem of cost: punishment can be too costly to execute, because the offender will fight back and inflict injury on those who try to punish him.
To solve these three problems, people will give up their powers in the state of nature for legislating, judging, and executing the law of nature (secs. 128-131). They will consent to enter a political society with governmental institutions for legislating, judging, and executing positive laws for the whole community that conform to the law of nature. This can solve the problem of knowledge, because the legislative power will publicly promulgate the laws. This can solve the problem of partiality, because the judicial power will decide legal cases through impartial and fair judges. This can solve the problem of cost, because the executive power will employ the collective force of the community to punish lawbreakers in ways that minimize the costs of punishment for individuals. All of this should serve the common good of the whole community--in securing the natural rights of all individuals to life, liberty, property, and the pursuit of happiness.
Of course, this goal can never be fully achieved, because the inevitable conflicts of interest that arise in every community will incline those with political power to use that power to favor their own interests over the interests of others, and thus government will often fail to promote the public good in securing the natural rights of all. If government becomes utterly tyrannical, then the rights of those being exploited are less secure under government than they would have been in the state of nature, because in a tyrannical government, the rulers can use the collective force of government to exploit the ruled (secs. 91-93).
If the government was imposed on the people by conquerors, and if the people never consented to that government, even if only by acquiescence, then they are still in a state of war in a state of nature, and they can exercise their natural executive power in violent resistance to their rulers (secs. 175-196J).
If the people did originally consent to their government, they can still rightly resist their government when it becomes tyrannical, because "the Obligations of the Law of Nature, cease not in Society" (sec. 135). And so if government does not conform to the law of nature, individuals have the natural right to resistance in meeting force with force.
The question will always be "Who shall be Judge whether the Prince or Legislative act contrary to their Trust?" Locke's answer is "The People shall be Judge." Or even "every Man is Judge for himself." They can "appeal to Heaven," as did Jephtha, which is to say that they can go to war against their government, and this dispute will be settled by battle (secs. 20-21, 239-243).
The assertion of natural rights depends on the forceful resistance to tyranny, which suggests that it is really true that might makes right. Natural rights emerge in history as those conditions for human life that cannot be denied without eventually provoking the natural human tendency of individuals to forceful rebellion against exploitation. Thus it is that individuals claim their executive power of the law of nature in punishing those who violate their natural rights.
But then we might wonder why Locke refers to this teaching about the natural executive power as a "very strange Doctrine" (secs. 9, 13). Leo Strauss and the Straussians--such as Michael Zuckert (1994)--have argued that Locke is intimating that this doctrine is "very strange" in the sense that it breaks with the traditional Aristotelian and Thomistic teaching about natural law. As a statement of the traditional teaching, Strauss (1953, 222) cites a passage in Aquinas's Summa Theologica (II-II, q. 64, a. 3), in which Aquinas answers no to the question "Whether it is lawful for a private individual to kill a man who has sinned?" Aquinas explains that only those with public authority to punish criminals can do this, not private individuals.
Strauss is silent, however, about the fact that a few pages after this passage, Aquinas answers yes to the question "Whether it is lawful to kill a man in self-defense?" (II-II, q. 64, a. 7). Killing in self-defense is not murder as long as one's primary intention is to save innocent life from attack, and killing the attacker is an unavoidable side effect. One can rightly kill an attacker in self-defense only when there is no non-lethal way to stop the attacker. Contrary to Strauss's claim, this seems to coincide with Locke's teaching that when innocent life is threatened by an attacker, and there is no way to call in a public authority to stop the attack, then at that moment one has been put into a state of nature where one can use one's natural executive power to kill the attacker, thus enforcing the right of self-preservation in the law of nature (secs. 11, 16, 18).
Strauss is also silent about Aquinas's argument that vengeance (vindicatio) is lawful and virtuous so far as it moves us to punish harmful wrongdoers, either in defending ourselves from harm or in avenging a harm (II-II, q. 108, aa. 1-3). Aquinas explains that vengeance belongs to the virtue of justice, and it expresses a natural inclination that we share with other animals who show an irascible power to retaliate against those who attack them. This natural inclination to punish those who threaten us with harm expresses "natural right" (ius naturale). (I have written a post on Aquinas's remarkable support for vengeance, in contrast to the turn-the-other-cheek teaching of the Sermon on the Mount.)
This natural law of self-defense and vengeance was recognized by Thomas Hobbes in The Leviathan, if only briefly, and then elaborated by Richard Cumberland in his Treatise of the Laws of Nature. Cumberland's account was a likely source for Locke's idea of the natural executive power, as suggested by Strauss (1953, 222, n. 83) and Zuckert (1994, 364-65).
Near the end of Chapter 31 of Leviathan, Hobbes has a short section on "natural punishments." Hobbes observes that natural laws are enforced by the natural punishments that arise as natural consequences of violating those natural laws. So, for example, injustice is punished by the violence of enemies. Or as he puts it in the Latin version of Leviathan, "those who use violence are punished by the violence of others; . . . and such are what I call natural punishments" (Hobbes 2012, pp. 572-73).
Cumberland's Treatise, first published in 1672, was one of the first attempts to refute Hobbes's theories. In arguing that Hobbes was inconsistent with himself in denying the obligations of the law of nature in the state of nature, Cumberland points out that Hobbes's remarks about "natural punishments" show how, even in the state of nature without any civil government, human beings are naturally inclined to vengeance against those who violate the law of nature, which provides the natural sanction for that law of nature. And since human beings are equal in their liberty in the state of nature, each individual would have the equal natural right to punish wrongdoers, so that the likely costs of wrongdoing would outweigh any likely benefits. Consequently, even those men who might be so evil as to lack any conscience that would recognize God's punishment of sin could not escape the punishment coming from human vengeance against injustice (Cumberland 2005, I.26, V.25).
The crucial point here is that for natural law to be truly natural, it cannot depend upon belief in divine law enforced by eternal rewards and punishments from God as the moral lawgiver. A purely natural law can be sanctioned by the natural human propensity to punish violent injustice, which expresses a natural inclination to vengeance shared with other animals.
This is an important element of the Lockean liberal argument for religious liberty and toleration. If the good moral order of any society depends on certain religious beliefs, this supports using legal coercion to enforce those religious beliefs. But if the natural moral law can be enforced by natural punishments, regardless of religious beliefs, then there is no justification for legally compelling belief in religious doctrines thought to sustain moral conduct. This point is clear in Locke's Letter Concerning Toleration, where he argues that it is unjust for the European conquerors of America to use legal coercion to compel the American Indians to convert to Christianity, because these "innocent Pagans" are "strict Observers of the Rules of Equity and of the Law of Nature, and no ways offending against the Laws of the Society" (Locke 2010, 40, 76-77). The natural right to punish those who violate the laws of nature enforces those laws without any need for religious beliefs about divine punishment.
Here, then, is the fundamental idea of Locke's natural executive power, implicit in the thought of Aquinas and Hobbes, developed by Cumberland, and elaborated by Locke.
Once we have traced this idea in the history of ideas, the next step for the serious student of political philosophy is to test the truth of this idea by formulating some testable predictions that follow from this idea, and then we must gather and assess the relevant empirical evidence. I can think of at least seven testable predictions.
1. In the human prehistoric foraging era and in ethnographies of foraging bands, we should see evidence for retaliatory violence by individuals acting against other individuals who harm them or threaten to harm them.
2. We should see evidence for vengeful violence in some nonhuman animals, particularly those closely related to humans.
3. We should see evidence for a natural human propensity to punish cheaters in experimental games.
4. We should see evidence for neural mechanisms in the human brain for first-party, second-party, and third-party punishment.
5. We should see evidence in human natural history for weapons and social mechanisms that reduced the costs of punishment.
6. We should see evidence in human history that the establishment of bureaucratic states during the agrarian era had a generally pacifying effect in reducing human violence.
7. We should see evidence in human history of resistance to tyrannical dominance and support for political institutions favoring some approximation to the equal liberty of the evolutionary state of nature.
I have written various posts on how Darwinian science might confirm these predictions. I will say more in some future posts.
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Cumberland, Richard. 2005. A Treatise of the Laws of Nature. Ed. Jon Parkin. Indianapolis: Liberty Fund.
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Waldron, Jeremy. 1989. "John Locke: Social Contract Versus Political Anthropology." Review of Politics 51: 3-28.
Zuckert, Michael. 1994. Natural Rights and the New Republicanism. Princeton, NJ: Princeton University Press.